(1) Field of the Invention
The present invention relates to solid polymer electrolytes processes for producing solid polymer electrolytes and precursors for solid polymer electrolytes. It relates also to electrical devices such as electrochromic devices incorporating such solid polymer electroclytes.
(2) Description of the Related Art
The formulation of polymer electrolytes for use in electrochromic devices is a long-standing problem. Attention has principally been concentrated on the use of polyethylene oxide containing lithium perchlorate as a conductive salt. Propylene carbonate has been used as a solvent in combination with polyethylene oxide.
Japanese Patent Specification No. 60037530 discloses a polymer electrolyte comprising polymethylmethacrylate, propylene carbonate and lithium perchlorate. The contents of polymethylmethacrylate is such that the electrolyte is gelatinous, having a consistency such that it is capable of being injected into an electrochromic cell.
Japanese Patent Specification No. 55-86070 discloses a battery electrolyte comprising polymethylmethacrylate, propylene carbonate and lithium fluoroborate in the form of a gel possessing elasticity produced by cooling a sol formed from the above materials. Battery electrolytes are not generally suitable for use in electrochromic devices and such suitability is not indicated in this specification. No conductivity figures are disclosed, nor are any fabrication methods which would lend themselves to the production of electrochromic devices.